Control of HIV drug resistance in older patients

描述（由申请人提供）：高效抗逆转录病毒疗法（HAART）极大地延长了艾滋病毒感染者的预期寿命，到2015年，美国一半以上的艾滋病毒患者将超过50岁。老年艾滋病毒患者经常出现合并症，如神经精神并发症和心脏、肾脏和肝脏疾病，需要额外的药物治疗。对于那些由于艾滋病毒耐药性而导致HAART失败的患者，最近开发的抗逆转录病毒类CCR5拮抗剂代表了另一种治疗选择。Maraviroc目前被批准用于使用CCR5作为辅助受体（所谓的R5菌株）感染耐药HIV病毒的患者，Vicriviroc正在进行III期临床试验。重要的是，与HIV非核苷逆转录酶和蛋白酶抑制剂不同，CCR5拮抗剂既不诱导也不抑制细胞色素P450 3A4，而细胞色素P450 3A4负责老年人常用药物的代谢。因此，CCR5拮抗剂可能为耐药R5 HIV感染的老年患者提供更安全的治疗选择，因为减少了药物与共给药药物相互作用的可能性。然而，最近的临床试验表明，R5 HIV可以对CCR5拮抗剂产生耐药性。对CCR5拮抗剂耐药的病毒通常获得使用拮抗剂结合的CCR5的能力，这表现为在药敏试验中不完全抑制病毒（平台期<100%）。在初步结果中，我们证明这些抑制平台受到CCR5密度的影响，在较低的CCR5密度下实现了更高的病毒抑制。这些结果首次表明减少CCR5可以控制病毒对CCR5拮抗剂的耐药性。我们的长期目标是通过靶向艾滋病毒生命周期中所需的细胞成分来控制艾滋病毒耐药性。本研究的目的是确定抗CCR5拮抗剂的R5 HIV在降低CCR5密度时恢复敏感性的机制。我们的假设是，抗CCR5拮抗剂的R5 HIV在降低CCR5密度时恢复敏感性，因为抗药病毒包膜蛋白对抗剂结合的CCR5的亲和力低于对游离CCR5的亲和力。我们有一个特定的目的：确定CCR5拮抗剂耐药的gp120对游离和结合的CCR5的亲和力，CD4和CCR5（游离和拮抗剂结合）关联的滞后期长度，以及CCR5拮抗剂耐药的R5 HIV感染的化学计量（每个病毒粒子参与的拮抗剂结合的CCR5分子的数量）。我们将通过结合实验、假病毒感染和细胞-细胞融合实验中CD4和CCR5（自由和拮抗剂结合）关联的滞后期长度，以及不同CCR5密度细胞系的假病毒感染的化学计量学来确定耐药gp120对游离和结合CCR5的亲和力。这一假设的成功证明将提示CCR5内化（即使用RANTES类似物）和抑制表达（即使用RNA干扰）作为潜在的治疗策略，以恢复对CCR5拮抗剂的敏感性，从而提高艾滋病毒患者，特别是老年人的生活质量。公共卫生相关性：根据2007年由国家艾滋病防治研究所和国家艾滋病研究所组织的艾滋病毒感染与老龄化问题讲习班，“确定对老年艾滋病毒感染者可能更有效的特定抗逆转录病毒药物或治疗策略至关重要”。对于由于病毒耐药性而无法治疗的老年HIV患者，新开发的CCR5拮抗剂代表了一种有吸引力的治疗选择，因为它们对耐药HIV具有活性，并且因为它们降低了毒性的可能性。由于HIV可以对CCR5拮抗剂产生耐药性，我们将确定耐药机制和潜在的控制策略，这将提高耐药HIV患者，特别是老年人的生活质量。

DESCRIPTION (provided by applicant): Highly active antiretroviral therapy (HAART) has dramatically increased life expectancy in HIV infection and by 2015 more than half of HIV patients in the U.S. will be older than 50. Elderly HIV patients often experience comorbidities such as neuropsychiatric complications and heart, kidney and liver disease, which require additional medications. For those patients failing HAART due to HIV drug resistance, the recently developed antiretroviral class of CCR5 antagonists represents an alternative treatment option. Maraviroc is currently approved for patients infected with drug-resistant HIV viruses that use CCR5 as a coreceptor (the so-called R5 strains) and Vicriviroc is in Phase III clinical trials. Importantly, CCR5 antagonists, unlike HIV non-nucleoside reverse transcriptase and protease inhibitors, neither induce nor inhibit cytochrome P450 3A4, which is responsible for the metabolism of many medications commonly used by the elderly. Thus, CCR5 antagonists may provide safer treatment options for elderly patients with drug-resistant R5 HIV infection because of the reduced potential for drug interaction with coadministered medications. However, recent clinical trials demonstrate that R5 HIV can develop resistance to CCR5 antagonists. Viruses resistant to CCR5 antagonists often gain the ability to use antagonist-bound CCR5, which is manifested by incomplete viral inhibition (plateau at <100%) in drug susceptibility assays. In Preliminary Results we demonstrate that these inhibition plateaus are affected by CCR5 density, with increased viral suppression achieved at lower CCR5 densities. These results provide the first indication that decreasing CCR5 can control viral resistance to CCR5 antagonists. Our long-term goal is to control HIV drug-resistance by targeting cellular components required in the HIV life cycle. The objective of this proposal is to determine the mechanism by which R5 HIV resistant to CCR5 antagonist regains sensitivity at reduced CCR5 density. Our hypothesis is that R5 HIV resistant to CCR5 antagonist regains sensitivity at reduced CCR5 density because the affinity of the resistant virus envelope protein is lower for antagonist-bound CCR5 than for free CCR5. We have one Specific Aim: To determine the affinity of CCR5 antagonist-resistant gp120 for free and bound-CCR5, the length of the lag phase for association of CD4 and CCR5 (free and antagonist-bound) and the stoichiometry (number of antagonist-bound CCR5 molecules engaged per virion) in CCR5 antagonist-resistant R5 HIV infection. We will determine the affinity of resistant gp120 for free and bound-CCR5 by binding assays, the length of the lag phase for association of CD4 and CCR5 (free and antagonist-bound) in pseudovirus infections and cell-cell fusion assays, and the stoichiometry in pseudovirus infection of cell lines with varying CCR5 densities. Successful proof of this hypothesis will suggest CCR5 internalization (i.e., using RANTES analogs) and inhibition of expression (i.e., using RNA interference) as potential therapeutic strategies to restore sensitivity to CCR5 antagonists and thus improve quality of live for HIV patients, especially for the elderly. PUBLIC HEALTH RELEVANCE: According to the 2007 Workshop on HIV Infection and Aging, organized among others by the NIAID and the NIA, "identification of particular antiretroviral drugs or treatment strategies that may be more effective in older HIV-infected individuals is essential". For elderly HIV patients failing HIV treatment due to viral drug resistance, the newly developed CCR5 antagonists represent an attractive treatment option because they are active against drug-resistant HIV and because they have reduced potential for toxicity. Since HIV can develop resistance to CCR5 antagonists, we will identify the mechanism of drug resistance and potential strategies for its control, which will improve quality of life for patients with drug resistant HIV, especially for the elderly.